Electric circuit interrupter



2 Sheets-SheetI 1 Inventor:

Charles H. Titus,

His Attcrh'n e5.

May 8, 1962 c. H. TlTus ELECTRIC CIRCUIT INIERRUPTER 2 Sheets-Sheet 2Filed Oct. l, 1958 Inventor: Charles H. Titus, bgm

7. ls Attorneg.

United States Patent() 3,033,964 ELECTRIC CIRCUIT INTERRUPTER Charles H.Titus, Havertown, Pa., assignor to General Electric Company, acorporation of New York Filed Oct. 1, 1958, Ser. No. 764,643 4 Claims.(Cl. 20G-166) This invention relates to electric circuit interrupters orbreakers, and more particularly it relates to an improvement in thecontact structure of a low voltage air circuit breaker.

One object of the invention is the provision of a circuit interruptercontact structure having a simple but elfective relatively stationarycont-act member that is both inexpensive to manufacture and convenientlyaccessible for the purpose of servicing.

A general object of the invention is to provide an 1mproved contactstructure of the character described hereinafter. U

In carrying out my invention in one form, an electric circuit breaker isprovided with a relatively stationary contact member comprising anelongated contact element pivotally supported intermediate its ends onan electroconductive fulcrum. Spring means is associated with one end ofthe contact element for establishing a biasing torque in the element,and suitable stop means is disposed to engage the other end of theelement to determine the limit of its pivotal movement under theinfluence 'of the biasing torque. The contact element forms acurrent-conducting joint with the fulcrum. The contact element isprovided with a contact surface at its other end, and a cooperatingmovable contact member is disposed for circuit making abuttingengagement with this contact surface whereby the relatively stationarycontact element is tilted on its fulcrum in opposition to the biasingtorque.

My invention will be better understood and its various objects andadvantages will be more fully appreciated from the following descriptiontaken in conjunction with the accompanying drawings in which:

FIG. 1 is a side elevation of .a circuit breaker contact structureembodying a preferred form' of my invention,

with the movable contact member shown in its closed circuit position;

FIG. 2 is a front elevation of a contact structure illustrated in FIG.l, with the movable contact member moved to its open circuit position;

FIG. 3 is a plan sectional view of the contact structure of FIG. 2 takenalong the line -3-3 and showing the stationary contact member with thecooperating movable contact member in an intermediate position; and

FIG. 4 is an exploded perspective view of the relatively stationarycontact member constructed in accordance with my invention together witha pair of cooperating movable contact arms and their supporting bracket.

Referring now to FIG. 1, I have shown an electric circuit interruptercomprising a base member 11, a relatively stationary Contact member 12mounted on the base, an electroconductive bracket 13 mounted on the basein spaced relation to the stationary contact member, a movable contactmember 14 pivotally supported by bracket 13 and disposed in cooperativerelationship with the stationary contact member 12, and actuating meanssuch as a crossbar 15 coupled to the movable contact member 14 formoving this member into and out of circuit-making engagement with thestationary contact member 12. The components 12, 13 and 14 comprise thecontact structure of one pole unit of an alternating or direct currentcircuit breaker or interrupter, and other similar pole units (not shown)can be mounted for gang operation on the base member 11 adjacent to thepole unit that has been illustrated in FIGS. l and 2.

The base member 11 supports the current-conducting 3,033,964 PatentedMay 8, 1962 studs of the breaker and the other breaker parts directlyconnected to the studs. As illustrated in FIG. 1, the base membercomprises a sheet 16 of electric insulating material of substantiallyuniform thickness. The sheet 16 is shaped to form a channel-shapedsection or depression at 17, and the bottom of this section is providedwith an aperture for snugly admitting and partially supporting an upperbreaker stud 18. For the purpose of the present description, the contactstructure 12-14 will be considered to be mounted on the front of thebase, and the upper breaker stud 18 is connected to a suitable electricpower source (not shown) located behind or to the rear of the base. Thecontact structure shown in the drawings and described herein toillustrate a preferred upper stud 118 is secured to the sheet 16 of basemember- 11 by suitable support means such as generally L-shaped angles19 and 20. The angles 19 and 20 are respectively disposed above andbelow stud 18 and are fastened thereto by three copper rivets 21 or thelike. The lower angle 20 is provided with a pair of tapped holes, 4and apair of appropriate bolts 22 and is used to secure this angle to thebase member 11. The supporting angle 19, which extends above the breakerstud 18 as is shown in FIGS. 1 and 4, serves as an arc runner incooperation with the stationary contact member 12. This angle isprovided with a stud 23 for securing it to the insulating sheet 16 ofthe base 11.

The end of breaker stud 18 extending forwardfrom the base member isdivided into two horizontally diverging branches whereby this stud inplan view has a generally Y-shaped appearance. In accordance with myinvention, the stationary contact member 12 comprises at least one pairof elongated elements or fingers 24, each linger 24 being pivotallysupported intermediate its ends on the outer end of a differentdiverging branch of the breaker stud 18 as is shown most clearly inFIGS. 3 and 4. For this purpose, I provide the outer ends of thediverging branches with generally cylindrical bearing surfaces 25,respectively, having centerlines oriented in Ia vertical direction asviewed in the drawings. Each bearing surface 25 is recessed so thatshoulders are formed at its upper and lower ends to prevent verticalmovement of the associated contact finger. If desired, the length of thebearing surface can be made suicient to accommodate more than onecontact inger 24 in side-by-side relation.

Each of the two bearing surfaces 25 at the outer ends of the divergingbranches of the breaker stud 18 provides a fulcrum or pivot for at leastone contact finger 24, and the pivotal connection between each contactfinger and the breaker stud forms a current-conducting joint. As can beclearly seen in FIGS. 2-4, the contact fingers 24 are respectivelysupported on opposite bearing surfaces 25 in opposing relationship withrespect to each other for pivotal movement in a common horizontal plane.The opposing or inner ends of the contact fingers are movable inseparate relatively short arcuate paths, and the opposing ends arerespectively provided with generally at complementary contact surfaces26 normally disposed in a common vertical plane as viewed in thedrawings.

The inner end of each contact linger 24 has an extension 27 disposed toengage a common stop 28 for determining the limit of the arcuatemovement of the con-Y tact surface 26 in one direction. The stop 28, asis shown in the illustrated embodiment of my invention, comprises acylindrical pin disposed intermediate the divergent branches of thebreaker stud18 and ixedly connected to the upper and lower supportingangles 19 and j 20. Thus, as best seen in FIGS. 3 and 4, the pin 28'isintermediate the opposing contact lingers 24 and isi.

A stop pin having a square cross-seccylindrical pin if desired, and Ihave found a square pin vto be advantageous from the point of view ofeasy assembly of the contact lingers 24 on the breaker stud 1S.

Associated withthe outer end 29 of each contact iinger 24 is suitablespring means, for example, the illustrated tension spring 30 which maybe anchored at one end to a fixed member such asy provided by thelaterally extending lugs 311 of the upper supporting angle 19. Springs30 establish oppositely directed biasing torques in the respectivecontact ngers 24 tending to move each contact surface 26 along itsarcuate pathV in a forward direction away from the base member 11, andsuch movement of 'the respective fingers is limited by the rstop pin 2S.The bias springs 36 also ,serve releasably to holdY each of the fingers24 against its respectivebearing surface of fulcrum 25. Theabove-describedstructure provides for a relatively limited deectionortilting ofthe `contact ngers in a rearward direction. t

The biasing torque is opposed and overcome and each ,contact nger 24 ofthe relatively stationary contact proximatcly perpendicular to the planedefined by the arcuate paths of the contact surfaces 26 of the Vlingers24. VThe actuating means provides actuating force for moving eachcontact surface 49 of member 14 intol and' out of circuit-makingabutting engagement with the con- 4 25. j In other Words, the line ofaction of the biasing spring force is placed relatively close to thefulcrum, and consequently the force exerted by the contact finger 24 onfulcrum 25 will be more than twice the amount of force that is appliedto contact surface 26 by the movable contact member 14.

It is particularly important for successful performance of the` contactmember 12 that the high Contact pressure between each contactiinger 24and its fulcrum 25 be maintained as the cooperating Contact surfaces 49and 26 part and an electric arc is drawnV during circuit opening orbreaking action of the 'contact structure. Toward this end, therelatively stationary contact member 12 is constructed soV that thelength of the moment arm (K of FIG. 3) of the resultant contact forceexerted on surface 26 with respect to fulcrum 25 just before thecooperating surface 49 disengages surface 26 is substantially equal tothe length of the moment arm (S in FlG. 3) of the resultant reactiveforce' at stop pin 28 with respect to fulcrum 25. By thus making themoment arm S approximately equal to the distance between fulcrum 25 andthe portion of surface 26 that is engaged by surface 49, the contactpressure at fulcrum 2S is not sig.- niiicantly reduced during therelatively short arcing pe- VVriod immediately following physicalseparation of the Y "movabley and relatively stationary Contact members14 tact surface 26 of a different contact finger with relatively Ylittle sliding movement taking place between the cooperating surfaces 26and 49.

During a circuit making operation, the contact surfaces 49 of themovable contact member 1,4 are jointly carried rearwardly from theiropen circuit position (FIG.V 2) intor substantially simultaneousengagement with both of the cooperating contact surfaces 26. FIG. 3shows the relative positions of the parts when circuit-making engagementis initially established, and further rearward established.V When thecontact structure is conducting;

alternating current, an electromagnetic force proportionalV to thesquare of current magnitude will tend to reduce the spacing betweenthese two parallel paths. As a result, a desirable increase in contactpressure is realized at the cooperating contact sur-faces 26 and 49, butan undesirable reduction in contact pressure tends to take place at Vthepointof contact lbetween each finger 24 and its fulcrum,2f5 In order toVensure'that there is always sucient forceV eifectiveto obtain Vagoodcurrent-conducting joint between thetingers 24 and breaker stud 18, withnegligible pitting or erosion at fulcrums: 25', I constructed andarranged the relatively stationary con# tact member -12 so that thearcuate path of the portion of each contact surface 26 engaged by aVcontact surface VV4 9of the movablercontact member is spaced from theassociated fulcrum 25 a distance .substantially greater than the lengthof the moment arm of the line of action of the tension spring 30, withrespect `to' the'fulcrumV and 12; Y t

The performance of the current-conducting joint between each relativelystationary contact finger 24 and its fulcrum 25 is further improved byminimizing the translation between these cooperating parts, that is, byensuring that the point of contact between each linger and its Vfulcrumdoes not shift appreciably as the movable Contact member 14 separatesfrom the stationary contact member 12 during a circuit breakingoperation. This desired result is achieved by the Vabove-describedstructure of the relatively stationary contact member 12. Furthermore,as is apparent from the drawings, the relatively stationary contactstructure is uncomplicated to manufacture and very convenientlyaccessible for servicing. By simply releasing the tension springs 30,the stationary contact fingers 24 can be easily and quickly removed andreplaced for the purpose of carrying out a routine main tenanceprocedure without anyl particular skill being required on the part ofthe maintenance man.

The electroconductive bracket 13 for supporting the movable Contactmember 14 is mounted on base member 11 by means of a pair of suitablebolts 32 or the like, as can be seen in FIGURES l and4 2. The bracket 13has a lower lip 33y provided with a hole for the purpose of connecting asuitable current-conducting member or another breaker stud (not shown)to the bracket. Part of the bracket 13 is disposed adjacent the frontsurface Vof the insulating sheet 16 of the base member 11, and

a rigid reinforcing member 34 is disposed adjacent the rear surface ofthe sheet 16 in overlapping relationship with bracket 13 and the lowersupporting angle 20, respectively. The reinforcing member 34 is providedso that the loading of the insulating sheet 16 in the area between thebracket 13 and the relatively stationary contact member 12 will be incompression rather than in flexure. A channel 3S of insulating materialis disposed intermediate the reinforcing member 34 and the rear of sheet16 to provide additional electrical insulation between the sides ofmember 34 and the fastening bolts 22 and 32.

The bracket 13 includes a pair of spaced-apart upstanding lugs 36 and 37projecting in front of base member 11. A removable pivot pin 38 issupported by the lugs 36 and 37, the axis of the pivot pin extending ina horizontal direction generally parallelV to the plane ofthe basemember'll as viewed in FIGS. l and 2. The pivot pin 38,

which passes through both of the lugs 36 and 37 and protrudes from theiroutwardly facing sides, respectively, is retained in place by areleasable clamp 39 connected to the pin intermediate the lugs. Theclamp 39 preferably comprises a resilient helical coil looselyencircling pin 38, the length of the helix corresponding approximatelyto the span between the lugs 36 and 37. 'Ihe opposite ends of the coilof clamp 39 extend tangentially therefrom and are arranged for movementbetween first and second cooperating positions. In FIG. 2 the ends areshown in a position wherein they releasably engage each other, and inthis self-locked position the circumference of the coil is contractedfor firmly grasping the encircled pin and preventing axial movement andremoval thereof. By separating the ends and permitting them to assumetheir other position in accordance with the resilience of the coil, thecircumference of the coil can be expediently expanded for assembling ordisassembling purposes.

The connection between the movable contact member 14 and the supportingbracket 13 will now be described with particular reference to FIGS. 2and 4. The movable contact member 14 comprises a pair of elongatedcontact arms 4t) and 41 arranged in generally parallel relation forjoint operation. One end 42 of the arm 40 is disposed adjacent theoutwardly facing side of the upstanding ,lug 36 and is rotatably mountedon a protruding portion of pivot pin 38; and one end 43 of the othercontact arm 41 is disposed adjacent the outwardly facing side of lug 37for rotatable mounting on the opposite protruding portion of the pivotpin. The connection between each movable contact arm 4t), 41 and theelectroconductive bracket 13 is arranged to provide three separatecurrent-conducting joints. The first such joint is provided by thebearing surfaces between the contact arm and the pivot pin 38 on whichit rotates, that is, between'pin 3S and the periphery'of a hole 44 whichhas been located in the one end 42, 43 to accommodate the pin 38. Thesurface of the pivot pin 38 and the periphery of hole 44 may be silverplated and burnished to ensure a wear-resistant, low electric resistancecurrent-conducting path.

The second current-conducting joint is obtained by providing theoutwardly facing side of each lug 36, 37 of the bracket 13 with asubstantially dat, smooth Vslide surface 45 disposed generallyperpendicular to the axis of the pivot pin 3S. Each slide surface 45 iscontiguous to a smooth, pertaining slide surface 46 provided on .therelatively broad inner side of the pivoted end 42, 43-of each movablecontact arm '40, 41, i.e., on the side of the contact arm facing thesupporting bracket 13. Each slide surface 46 is disposed generallyparallel to the respective adjoining slide surface 45 of the bracket 13,and therefore all of the slide surfaces 45 and 46 are substantiallyperpendicular to the axis of pivot pin 38 which corresponds to the axisof rotation of the movable contact arms 4t) and 41.

The slide surface 46 of each movable contact arm includes a raisedsection which, as can best be seen in FiG. 4, preferably comprises aportion of a cylinder. The crest of this raised section is oriented sothat it extends in a direction substantially perpendicular to thelongitudinal centerline of the contact arm, and it is intersected by thehole 44 provided for pivot pin 38. 'Ihe crests of the raised sections ofthe two slide surfaces '46 respectively cooperate with and arecontiguous to the slide surfaces 45 of bracket 13, and pivotal movementof the contact arms on pin 38 causes each crest to slide over theassociated slide surface of the relatively stationary bracket 13. Thecontiguous portions of each pair of cooperating slide surfaces define aline contact which provides the second current-conducting joint betweeneach movable contact arm and the supporting bracket. Of course, as analternative to the specific arrangement illustrated and described above,a raised section could -be located on each of the slide surfaces 45 andthe slide surfaces 46 could be made substantially flat.

Contact pressure at the joints formed by the respective pairs ofcontiguous slide surfaces 45 and 46 is maintained by means of anelectroconductive spring member 48 which preferably comprises a U-shapedspring clip. As indicated in FIGS. 1 and 2, the resilient upstandinglegs of the clip 48 are split for respectively bearing against the outersides of the pivoted ends 42 and 43 of the contactv arms 40 and 41 atpoints disposed onl opposite sides of the pivot pin 38. Theelectroconductive spring member 48 is secured to the bracket 13, andsince it also is iri engagement with each movable contact arm itprovides the third current-conducting joint. 48 applies a sidewise forcewhich maintains contact pressure at the contiguous surfaces of bothpairs of cooperating slide surfaces 45 and 46. This force issupplemented by an electromagnetic force whenever the movable contactmember 14 is conducting current. Whenever the parallel contact arms `40and 41 conduct alternating current, a magnetic force is establishedtending to reduce the spacing between these two arms and therebyestablishing additional contact pressure at the contiguous slidesurfaces, the magnitude of this sidewise force being proportional to thesquare 'of the current magnitude.

The diameter of the hole 44 in the pivoted ends of the movable contactarms is made slightly greater than the diameter of pivot pin 38. Thisarrangement permits'tlie contact arms 40 and '41 to rock on pivot pin38. The crests of the raised sections of the slide surfaces 46 pro-Videpfulcrums for the rocking movement of the arms 40 and 41,respectively, and this rocking movement takes place in a planeperpendicularv to the planes of pivotal movement of the arms. Thisarrangement allows for a certain degree of misalignment of the variousparts and a liberal manufacturing tolerance without adversely affectingthe positiveness of the electric contact between the movable elementsand the supporting bracket 13. Y

By utilizing three parallel current-conducting joints for each of thetwo parallel arms ofthe movable contact member 14, the overall electricresistance of the pivotal connection has been efficiently reducedthereby significantly decreasing temperature rise. In this manner it ispossible to obtain a successful contact structure without conventionalflexible braids or conductors.

' In the illustrated embodiment of my invention, the corresponding freeends of the contact arms 40 and 41 areV provided respectively withtransverse contact surfaces 49 disposed for abutting engagement withthecontact surfaces 26 of the relatively stationary contact fingers 24.Rotaryor pivotal movementof the contact arms on pivot pin 38 carries thecontact surfaces 49 through arcuate paths which define vertical planesintersecting at approximately right angles the horizontal plane ofmovement of the relatively stationary contact surfaces 26, as viewed inthe drawings. This arrangement permits the convenient utilization ofmore than one stationary contact finger for each movable contact arm,whereby more than two separate points of circuit-closing engagement canbe provided between the movable contact member 14 and the relativelystationary contact member 12.

The cooperating contact surfaces 26 and 49 preferably are made of silvertungsten carbide material'which will successfully perform the continuouscurrent-carrying function of the contacts and also the required circuitmaking and breaking duty without appreciable contact erosion or pittingor contact welding as a result of electric arcing. Therefore it is notnecessary to provide separate arcing and main contacts. With the variousparts shown in FIGS. l and 2 appropriately dimensioned, the contactstructure will safely carry at least 225 amperes continuously at 600volts A.C. and the same contact structure can be modified to carry atleast 600 amperes continuously merely 'by changing the relativelystationary contact member 12 so that two contact fingers (24) arerespectively disposed adjacent those shown and by appropriatelyextending the contact surfaces 49 of the movable contact arms. A

' In orderl to obtain a compact arrangement at thereooperating contactsurfaces 26 and 49, the contact arms In addition, spring membery FIGS;-2 and 4,v this has beenaccomplishe'd by axially offsetting the freeends of the contact arms withI respect to the pivotally connected ends42' and 43, respectively. In n addition; the contact arms are oppositelyoffset at interrmediate portions 50. As is indicated iii-FIG. 4,*theodset portion 50j of each arm is providedwith a transverse hole -1 thecenterline ofwhich is oriented parallel to the pivotpin 38.

A11 actuating member such asa cylindrical mpelling shaft SZis rotatablydisposed in the holes 51' of bothcontact arms 40 and 41and by this meansactuating force arms, .are respectively disposedy to extend inoverlapping relationship Wit-h'the lugs 36-and 37 of bracket 13. ln thismanner, the current-conducting jointsformedby the two pairsV of.contiguous slide surfaces 45 andf are shielded from the electric arcandare products which may be-produced during circuit'breaking action. ofthecontact structure; The protrusions 53- will prevent particles offoreignv matter generated during circuit breakingacton fromenterngthesejoints by straight-line paths from the area of.. arc interruption.Su'ch'foreign matter, if permittedto enter the joint, could causeexcessiverwear and increasedcontact resistance. v r

The-impelliug shaft 52 titsV relatively loosely in theholes 51 of theoffset portions SDofth-e movable contact arms 401 and41, whereby eacharmican slideon shaft 52. While rockingon pivot pin 381 Thus the contactsurface 49 of each a-rmfisfree to movein'- a lateral-or transversedirection,` and suchlateralL movement' is controlled byresilient y meansassociated withthe contact arm. Asis shownin FIG. 2the resilient meanspreferably comprises a helical spring54 disposed onimpellingfshaft 52intermediate the' contact arms-40and 41. The springl 541applieslatransverse force to reach-contact arm and'establishes ineacharm arelatively Weak biasing torque with respect tothe pivot'provided by theline contactvr atthe joint formed by the associated pair of contiguousslide surfaces and` 46'.4N Thisbiasing torque isinja direction-'tendingtovspread apartthecontact arms. .Such movement-of-each Contact armisstopped' and itsnormalposition is determined by aA bushing 55 disposedonlshaft SZV-between a retaining ring 56 crit-he like andthe circularouter side of theV offset por,-A

`tion of the arm. See FIG. 2.

kDuring-'circuit making action of the` contact structure,"

each contact surface 49 comes into abutting engagement v to theresilient means Sli-'andtothe fulcruml provided by the crest of theraised section of the contiguous slideV surfaces Yi5 and 46,'themovablecontactarm is able tor yield to,th-is transverse force, andcontactsurfa'ce` 49 moves laterally while following the arcuate pathoflcontact surface 26,. As a result, the relative movement between thecooperating contact surfaces 26 and 49 is reduced thereby reducing theamount of friction between these cooperating surfaces and.improving-the` performance of the contactv structure.

Y The movable contact member 14 is coupled to the ac.- tuating means orcrossbar 15byv means of an actuating y member 57V coupled to theimpellingshaft 52 and prefer-V ably comprising a generally U-shapedconnecting link securelyfastened-to the crossbar. Eachleg-of theconnecttated to any one of six angular positions.

the pivot pinV 38 as shown in FIG'. 1, and ythus the cross- Y bar 15 issupported for pivotalmovement by pin 38. End

portions 59 of impelling shaft 52 extend laterally from the contact arms40 and 41 andare made eccentric with respect tothe cylindrical body ofthe shaft, as is Vshown "in FIGS. 1 and 2. lThe endportions 5,9 arecoupled to the connecting link 57 in a manner permitting controlledrotation of the shaft 52. This has been done by providing eachendportion 59 with flat sides forming a hexagon, parallel sides of thehexagon being positively but resiliently locked between a shoulder of aconnecting link 57 and a cooperating cantilever ilat springV 6@ carriedby link 57. See FIG. 1.

By means of a conventional open-end wrench applied to the hexagonal endportion 59, the shaftSZmay be ro- In each of these sixpositions, themovable contact member 14 is located in a different relative angularposition with. respect to the crossbar 15 and with respect to therelatively stationary'contact member 12. The purposeof this adjustmentis to accurately establish theV fully closed position of the movablecontact member regardless of liberal manufacturing tolerances; wherebythe desired amount of contact wipe can be precisely obtained.

.The crossbarl is connected to a circuit breaker operating mechanism bymeans of another link 61 and a connecting member 62. The.operating`mechanism, which has not been shown, maybe of any suitable type formovingV theconnectingmember 62V in a generally horizon- 4tal direction(asviewedin FIGS. -1` andV 2) thereby reciprocally moving-the crossbar15 about. its'pivot between first and secondi relatively fixedpositions.v The crossbar 15 may be extended across the width of thecircuit breaker for connection in a similar manner to other pole unitsof a multipole'circuit breaker. An isolating barrier 63 of insulatingmaterial is shownvmounted on the. crossbar 15 in FIG. 2. Other barriers64 are provided for the purpose of isolating thevariouscurrent-conducting parts of the illustrated poleA units from thecorresponding parts of adjacent pole units and from ground. A suitablearc chute,V not showninthe drawings, may be mounted on the basememberlltoenclose the cooperating contact surfaces. 26 and 49 for theconventional purpose ofarc extinction.

While I have shown and describedV a preferred'rforrn of my invention byway of' illustration', many modifications Will occurto those skilled inthe art.

modiiications as fall within the true spirit and scope of my invention.l y

What I claim as new and desire to secure by Letters Patent of the UnitedStates is: k

l. In a contact structure of anelectric circuit interrupter; a basemember; a relatively stationaryV contact mounted on the baseV comprisingan elongated contact element pivotally supported intermediate its endson a fulcrum, spring means associated with one end of the contactelement for releasably holdingV the element against said fulcrum and forestablishing a biasing torque in the element, and stop means disposed toengage the other end o f the element to determine the limit of itspivotal move-Y ment under the influence of the biasing torque, the ystopmeans being disposed so that the moment arm of the resultant reactiveforce at the stop means with respect tothe fulcrum 'is a predeterminedlength, said elementhav-4 ingV at said other end a generally at contactsurface spaced from the fulcrum a distance approximately equal to saidpredetermined length; a bracket mounted on the' base in spaced relationto the stationary contact; aV movable contact member supported Yby thebracket for movement into circuit making engagement with the contactingflink? is provided with an extension 58 connected-to 75. able contactmember for moving said member.

Y Therefore, I contemplate by the concluding claimsrto cover all such 2.In the contact structure of an electric circuit interrupter: a basemember; a relatively stationary contact member mounted on the base andincluding at least one pair of opposing contact ngers supportedintermediate their respective ends on spaced-apart fulcrums for pivotalmovement in a first common plane, spring means' associated with saidcontact fingers for establishing oppositely directed biasing torques inthe respective fingers, and a stop pin located intermediate the fingersfor abutting engagement with the opposing ends of both fingers todetermine the limit of pivotal movement of each finger under theinliuence of its biasing torque, the opposing ends of the lingers beingrespectively provided with generally fiat contact surfaces normallydisposed in a second common plane which is perpendicular to said firstcommon plane; a bracket mounted on the base in spaced relation to thestationary contact member; a movable contact member supported by thebracket for movement into circuit making abutting engagement with thecontact surfaces of both of the relatively stationary contact fingersthereby tilting the lingers on their respective fulcrums in oppositionto their respective biasing torques; and actuating means coupled to themovable contact member for providing actuating force therefor.

3. In the contact structure of an electric circuit inter-` rupter: abase member; a relatively stationary contact comprising anelectroconductive member mounted on the base and disposed to provide afulcrum, a contact linger pivotally supported intermediate its ends onthe fulcrum to form therewith a first current-conducting joint, springmeans associated with one end of the contact finger for establishing abiasing torque in the finger, and stop means disposed to engage theother end of the nger to determine the limit of its pivotal movementproduced by the biasing torque, the stop pin being disposed so that themoment arm of the resultant reactive force at the stop pin with respectto the fulcrum is a predetermined length, the finger having at saidother end a generally fiat contact surface spaced from the fulcrum adistance approximately equal to said predetermined length; anelectroconductive bracket mounted on the base in spaced relation to thestationary contact; a movable contact member rotatably connected to thebracket for movement into circuit making engagement with the contactsurface of the relatively stationary contact finger and thereby tiltingthe finger on its fulcrum in opposition to the biasing torque, theconnection between the bracket and the movable contact member includingcontiguous slide surfaces disposed generally perpendicular to the axisof rotation to form a second current-conducting joint; and actuatingmeans coupled to the movable contact member for rotating said member,

4. In the contact structure of an electric circuit interrupter: a basemember; a relatively stationary contact comprising an electroconductivemember mounted on the finger being movable at one end in an arcuatepath,

spring means associated with the other end of the finger forestablishing a biasing torque in the finger tending to move said one endin a given direction along said arcuate path, and stop means disposed toengage the finger near said one end to determine the limit of thearcuate movement of said one end in said given direction; anelectroconductive bracket mounted on the base in spaced relation to thestationary contact; a movable contact arm rotatably connected to thebracket for movement at one end along an arcuate path, said arm beingdisposed in relation to the contact finger so that the respectivearcuate paths define intersecting planes, the connection between bracketand arm including contiguous slide surfaces disposed generallyperpendicular to the axis of rotation to form `a secondcurrent-conducting joint, one of said surfaces being substantially atand the other being raised so that the contiguous portions of thesurfaces define a straight line; an electroconductive spring memberengaging the bracket and the movable contact arm to maintain contactpressure at the second joint and to provide another current-conductingjoint with the movable con,- tact arm; and actuating means coupled tothe movable contact arm to move the one end of said arm into and out ofcircuit making engagement with the one end of said relatively stationarycontact linger.

References Cited in the le of this patent UNITED STATES PATENTS 856,737Sill June 11, 1907 1,935,512 Massey Nov. 14, 1933 1,978,246 BauerschmidtOct. 23, 1934 2,090,754 Graves Aug. 24, 1937 2,095,554 Maseng Oct. 12,1937 2,347,030 Crabbs Apr. 18, 1944 2,471,608 Caswell May 31, 19492,546,366 Lindae Mar. 27, 1951 2,581,181 Faure Ian. 1, 1952. 2,627,559Metzel Feb. 3, 1953 2,636,961 Schneider Apr. 28, 1953 2,650,284Volgovskoy Aug. 25, 1953 2,691,085 Beatty Oct. 5, 1954 2,790,050 Fawdreyet al Apr. 23, 1957 2,918,552 Fust Dec. 22, 1959 2,938,986 BaskervilleMay 31, 1960 FOREIGN PATENTS 566,402 France Nov. 22, 1923 578,057Germany June 9, 1933 537,356 Great Britain June 18, 1941

